java - ButtonGroup 空指针异常

Question

我创建了一个方法，该方法将清除以前对我的 ButtonGroup 所做的任何选择，该选择由单选按钮组成

    public void resetRadioButtons() {

    if (group.getSelection() != null) {
        group.clearSelection();
    }
    else {

    }

}

该组在此处实例化：

        final ButtonGroup group = new ButtonGroup();
        group.add(radioAnswer1);
        group.add(radioAnswer2);
        group.add(radioAnswer3);
        group.add(radioAnswer4);

调用该方法时，它会在该行给出 NullPointerException：

if (group.getSelection() != null) {

我不知道我做错了什么。提前致谢。

Answer 1

很可能您正在隐藏group变量。尝试更换

final ButtonGroup group = new ButtonGroup();

和

group = new ButtonGroup();

Answer 2

If the exception is indeed on this line

if (group.getSelection() != null) {

(and not in getSelection() itself),
then group is null there.

Make sure it's initialized first.